diff --git a/chip-fel-flash.sh b/chip-fel-flash.sh
index 7f179af..6ba5ddb 100755
--- a/chip-fel-flash.sh
+++ b/chip-fel-flash.sh
@@ -2,21 +2,7 @@
 
 SCRIPTDIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 
-onMac() {
-  if [ "$(uname)" == "Darwin" ]; then
-    return 0;
-  else
-    return 1;
-  fi
-}
-
-filesize() {
-  if onMac; then
-    stat -f%z $0
-  else
-    stat --printf="%s" $0
-  fi
-}
+source $SCRIPTDIR/common.sh
 
 FEL=fel
 
diff --git a/common.sh b/common.sh
new file mode 100644
index 0000000..298c115
--- /dev/null
+++ b/common.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+onMac() {
+  if [ "$(uname)" == "Darwin" ]; then
+    return 0;
+  else
+    return 1;
+  fi
+}
+
+filesize() {
+  if onMac; then
+    stat -f%z $0
+  else
+    stat --printf="%s" $0
+  fi
+}